APPARATUS FOR DRYING EXTENSIVE SURFACES

Abstract: Apparatus is disclosed for drying extensive surfaces, comprising: means for transporting the entire apparatus across the surface (2), and an air knife (20) directed at the surface (22), the air knife comprising one or more nozzles; and means (56) for delivering air to the nozzle(s) at a high volume flow rate and low pressure. In a preferred arrangement, the or each nozzle has an outlet comprising an elongate slot. The apparatus may be used to clear surface water from roads, or sports areas before laying tarmac or markings, or for drying pitches whether grass or synthetic. Other uses may well occur to the reader. In another arrangement for drying slots or grooves in a road surface before sealing with tarmac, the nozzle is preferably not in the form of an elongate slot, e.g. is square or round in cross section. It is possible that the surface will remain damp if treated only with the air knife and, against this possibility, a much preferred embodiment of the invention includes an arrangement to heat the air supplied to the nozzle.

Description: APPARATUS FOR DRYING EXTENSIVE SURFACES This invention relates to apparatus for drying extensive surfaces. The background to the invention will be explained in relation to a problem which occurs in a particular field, although it will be recognised that the invention is not limited to that field and may be utilised in other fields. Road markings are laid as a hot molten thermosetting plastics compound, which includes a filler. As the compound cools it sets to a solid which is intended to adhere to the surface of the road. Unfortunately, even a very small amount of moisture on the road surface prevents the adhesion so that many working hours are lost each year while road marking gangs wait for the surface to dry. One attempt to dry the surface involves a hollow lance with a plenum chamber at one end from which open a series of small orifices. Air under high pressure is supplied to the plenum chamber by a compressor which is readily available to a road working crew. The plenum chamber is also supplied with a fuel, e.g. propane, which is burnt in the compressed air in the chamber. The arrangement does not work very well and the apparatus produces a great deal of noise which is not acceptable to the workforce. Against this background, in accordance with the invention, there is provided apparatus for drying extensive surfaces, comprising: means for transporting the entire apparatus across the s-uε-face, and an air knife directed at the surface, the air knife comprising a one or more nozzles; and means for delivering air to the nozzle(ε) at a high volume flow rate and low pressure. In a preferred arrangement, the or each nozzle has an outlet comprising an elongate slot. The arrangement efficiently strips water off the surface and the noise may be kept down to a level acceptable to the work force. The apparatus may be used to clear surface water from roads, or sports areas before laying tarmac or markings, or for drying pitches whether grass or synthetic. Other uses may well occur to the reader. In another arrangement more effective for drying slots, crack or joints on a road surface before sealing with tarmac a rubberised filled bitumen product, the nozzle is preferable not in the form of an elongate slot, e.g. is square or round in cross section. Despite the efficiency with which the apparatus may strip water off the surface it is possible that the surface will remain damp if treated only with the air knife and, against this possibility, a much preferred embodiment of the invention includes an arrangement to heat the air supplied to the nozzle. Surprisingly, sufficient heat can easily be provided to dry the surface completely, or sufficiently to lay road markings. In one preferred form, the means for delivering air to the slot includes a blower driven by a motor mounted in or on the apparatus. The blower can be a standard product. The motor may be a petrol or diesel unit. For efficiency^the total cross sectional area of the nozzle(s) at its or their outlet is preferably approximately equal to the cross sectional area of the outlet of the blower through which the air is delivered. The arrangement to heat the air preferably includes a heater comprising chamber, a burner to burn fuel in said air in the chamber, and means mounted in or on the apparatus for storing the fuel and supplying it to the burner. Previous proposals for air knives to use heated air have used electric heaters. That may be adequate for static apparatus in a factory environment, but is not suitable for mobile apparatus which is moved across extensive surfaces, e.g. many miles of roadway preparatory to marking a line or sealing a slot or groove. In an alternative preferred form, a jet engine constitutes both the arrangement to heat the air and also the means for delivering air to the slot. The engine may be a fan jet. The apparatus may be automotive or may be hand held or mounted on, say, wheels so that motive power is provided by a pedestrian. Especially, but not exclusively, in the case of an automotive apparatus, means are preferably included for treating the dried surface e.g. for laying a thermosetting compound on the dried surface. The thermosetting compound may comprise tarmac or a compound for marking lines on the surface. Embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a—aide view of a first road marking machine embodying the invention; Figure 2 is a pictorial view, partly broken away, of an arrangement of air knives of the apparatus of Figure i; Figure 3 is a sectional view of a heater of the apparatus of Figure 1; Figure 4 is a cross section through an air knife of the apparatus of Figure 1 Figure 5 is a scrap view on arrow A of Figure 4; Figure 6 is a side elevation of a second road marking machine embodying the invention; Figure 7 is a plan view of part of burner and nozzles of the machine of figure 6; Figure 8 is a side elevation of a pedestrian controlled road drying machine embodying the invention; and Figure 9 is a scrap view of a modification of the machine of Figure 8. Referring to the drawings, a road marking vehicle 2 having road wheels 4, is driven by an engine 6, and is controlled by an operator seated at a position 8 where a steering wheel 10 and other controls are located. As is conventional the vehicle has a heated hopper 12 for the thermosetting compound to be laid, and a laying head 14, for example an extrusion shoe (illustrated) or a screed box. As the vehicle is driven along the road, the laying head is selectively operated to lay the compound on the road so as to provide the desired markings. The vehicle illustrated additionally has three air knives 20, illustrated " ~generally in Figure 1 and more particularly in Figures 2 and 4 and 5. The air knives 20 are directed downwardly and forwardly at the road 22 ahead of the track that the laying head will follow. Referring to Figure 2, each air knife comprises a cylinder 24 closed at each end to provide a plenum chamber 26. An outlet is provided in the form of a rectangular slot 28 between plates 30 which direct air at high volume and low pressure downwardly and forwardly at the road 22. In order to operate more effectively, the plates should be manufacture to resist distortion from the high temperatures which will be obtained by the heating arrangement to be described. In the example shown, the plates are manufacture from thick plates of high grade stainless steel and, additionally, are bridged at intervals by weld so as to maintain their spacing. An inlet manifold 32 is provided in the form of a tapering tube to supply air to the plenum chambers. At its inlet end the manifold has a cross sectional area approximately equal to the total cross sectional area of all three slots 28. The manifold tapers towards the most forward of the air knives so that at its most forward end, it has a cross sectional area approximately equal to the area of the slot of that air knife. At the intermediate air knife the manifold has a cross sectional area approximately equal to the area of the outlet slots of two air knives The air knives 20 are mounted in a frame 40 which is supported above the road by four castors 42 so that the air knives are positioned a predetermined distance from the road surface. The franae 40 is attached to the vehicle by arms 44 pivotally connected at one end to the vehicle (not shown) and at the other 46 to the frame. The air knives are thus moved along the road by the vehicle ahead of the laying head. The manifold inlet 34 is connected via a heater 54, and a flexible pipe 52 to the outlet of a blower unit 56. The cross sectional areas of the pipe 52, and thus the manifold inlet 34 and the total area of the slots 28, are chosen each to approximately equal the cross sectional area of the outlet 58 of the blower 56. The blower is driven by a petrol engine 60, the two being mounted on a platform 62 attached to the vehicle. A cross section of the heater is shown in Figure 3. The heater has a chamber 70 which expands from an inlet 72, which has a cross sectional area equal to that of the pipe 52, to a larger cross sectional area in which a burner 74 is mounted by a perforated conical support 76. Propane, or in other examples other fuel, is supplied to the burner from a container 78 mounted at the rear of the vehicle. The fuel is ignited by a spark plug 80. A flame failure device including a sensor 82 operates to cut the fuel supply if the temperature drops indicating the flame has gone out. At its outlet 84 the chamber 70 reduces in cross sectional area to match that of the inlet to the manifold 32. Operation of the engine 60 to drive the blower 56 produces a high volume flow of low pressure air at the air knives 20 distinct, say, from the low volume high pressure air supply which is pro ided by a compressor. The air knives will clear loose water from the road as the vehicle is driven at a surprisingly high rate. Without operation of the heater the road would remain damp, although free of loose water, and prevent the adhesion of road marking compound. The drying apparatus may have utility in other applications, however. One example is to clear loose water from, say, a sports pitch or race track. Operation also of the heater will dry the surface more or less completely: sufficient to allow road markings to be laid. In one example we found the temperature of the air at the outlets of the air knives to be about 750°C. An another example is illustrated in part in Figures 6 and 7. Here the main difference is an improved burner 74. this is in the form of a ring burner from which we have obtained a temperature at the outlets of the air knives of about 900°C. In other examples, the low pressure high volume air could be both provided and heated by a fan jet. In yet other examples, the apparatus may be controlled by, or pushed by, a pedestrian operator. Such an arrangement is illustrated in Figures 8 and 9. Here the primary function of the apparatus is to dry the surface, e.g. the road 22. Subsequent treatment of the surface, e.g. marking with a line, sealing a slot or groove, laying tarmac etc, would be carried out separately by hand or by another machine not illustrated. The apparatus is mobile, having a tubular chassis 100 supported on a pair of wheels 102, rotatable about a common axis, and a pair~<ef castor wheels 104. The burner 54, pipe 52, blower 56, engine 60 and gas supply 78 are mounted on the chassis 100 and are similar to those of Figure 1, except that the engine is gas fuelled from the same supply 78 as the burner. The specific arrangement of air knives is different in that a manifold 106 feeds heated air to two air knives 20 mounted one behind th other. A modified air knife 20 is illustrated in Figure 9. Here a single outlet 108 is provided from a pipe 110. The outlet may have the same cross sectional shape as the pipe and in particular does not have the form of an elongate slot illustrated in the other embodiments. As there is no need to distribute the airflow across an elongate slot, no plenum chamber is required. The arrangement is especially useful for drying slots or grooves preparatory to sealing them with rubberised filled bitumen product. Other pedestrian control apparatus (not illustrated) may be automotive and/or may include equipment for treating the surface, e.g. for marking a road with lines.

Claims: CLAIMS 1. Apparatus for drying extensive surfaces, comprising: means for transporting the entire apparatus across the surface, and an air knife directed at the surface, the air knife comprising a one or more nozzles; and means for delivering air to the nozzle(s) at a high volume flow rate and low pressure. 2. In plant for treating extensive surfaces, apparatus for drying the surface to be treated comprising an air knife directed at the surface, the air knife comprising a one or more nozzles; and means for delivering air to the nozzle(s) at a high volume flow rate and low pressure 3. Apparatus as claimed in claim 1 or 2, including an arrangement to heat the air supplied to the nozzle. 4. Apparatus as claimed in any preceding claim, wherein the means for delivering air to the slot includes a blower driven by a motor mounted in or on the apparatus or plant. 5. Apparatus as claimed in claim 4, wherein the total cross sectional area of the nozzle(s) at its or their outlet is approximately equal to the cross sectional area of the outlet of the blower through which the air is delivered. 6. Apparatus as claimed in any preceding claim, in which the or each nozzle has an outlet comprising an elongate slot. 7. Apparatus as claimed in claim 3 or any preceding claim dependent thereon, wherein the arrangement to heat the air includes a heater comprising chamber, a burner arranged to burn fuel in said air in the chamber, and including means mounted in or on the apparatus for storing the fuel and supplying it to the burner. 8. Apparatus as claimed in claim 3, wherein a jet engine constitutes both the arrangement to heat the air and also the means for delivering air to the slot. 9. Apparatus as claimed in claim 8, wherein the engine is a fan jet. 10. Apparatus as claimed in claim 2 or any preceding claim dependent thereon, including means for laying a thermosetting compound on the dried surface. 11. Apparatus as claimed in claim 10, wherein the thermosetting compound comprises a rubberised filled bitumen product or a compound for marking lines on the surface. 12. Apparatus as claimed in any preceding claim, wherein the apparatus is automotive. 13. Apparatus for drying extensive surfaces substantially as hereinbefore described with reference to the accompanying drawings.

Inventors: BRADFORD DAVID HUGH, GLENDINING PETER HAYWARD, BRADFORD, DAVID, HUGH, GLENDINING, PETER, HAYWARD
Applicants: BRADFORD DAVID HUGH, GLENDINING PETER HAYWARD, GLENDINING ROADMARKS LTD, S & S GMBH, BRADFORD, DAVID, HUGH, GLENDINING ROADMARKS LTD., GLENDINING, PETER, HAYWARD
Application year: 1994
Main classification: E01C23
IPC codes: E01C23